Compact Filtering Microstrip Antenna With Enhanced Out‐of‐Band Suppression

ABSTRACT A compact filtering microstrip antenna with high selectivity and enhanced out‐of‐band suppression is presented in this article. Significantly reduced dimension is realized by incorporating a capacitive blind‐via fence on the radiating apertures of a square microstrip antenna. Then, two pairs of quarter‐wavelength open‐ended slots are etched onto the patch to generate two radiation nulls precisely positioned at the upper and lower band edges. Additionally, two U‐shaped slots are strategically employed at the center of the patch to mitigate strong current distribution, thereby significantly improving out‐of‐band suppression. Finally, an out‐of‐band suppression of 12.9 dB is attained up to 2.1 f 0 ( f 0 is the center frequency). As a proof of concept, a prototype with a compact size of 0.19 λ 0 × 0.19 λ 0 is fabricated and tested, showing a −10 dB‐impedance bandwidth of 1.85 ~ 1.98 GHz and an average gain of 6.4 dBi. With the advantages of compact size, high selectivity and wideband out‐of‐band suppression, the proposed filtering antenna exhibits potential usages in compact wireless communication system.